In the orthographically correct Portuguese phrase:
No silencio (In the I silence),
what is meant is:
No silêncio (In the silence).
There are several substantives in Portuguese that have verb forms that in singular present (1. person singular if ending when -o, 3. person singular when ending in -a), are orthographically equal up to missing accent marks; most of them terminating in
-ância, -êncio, -ário, -ática
and their corresponding verb forms
-anciar, -enciar, -ariar, aticar.
silêncio/silenciar, substância/substanciar, dicionário/dicionariar, gramática/gramaticar.
Therefore, how about checking if the supposed substantive is preceded by an article, that is, if it is preceded by the regular expression
Lightproof in LibreOffice does something similar.